1. Field of the Invention
The present invention relates to an anti-skid control system for vehicles which is capable of preventing skidding of a vehicle caused by the locking of the wheels when the running vehicle is braked and the braking pressure applied to the wheels exceeds a certain value determined by the coefficient of friction between the wheels and the road surface.
2 Description of the Prior Art
Conventional anti-skid control systems of the above type are designed for accomplishing a real time control in which the speed of a vehicle body is detected to maintain the wheel speed at a value lower then the vehicle body speed by for example about 20%, and a predictive control is accomplished in which the wheel speed for example is detected to prevent locking of the wheels. In other words, to prevent locking of the wheels due to the excessively applied braking pressure, the wheel speed immediately before the braking of the vehicle is stored and at the same time this wheel speed is gradually decreased in accordance with predetermined control patterns to obtain a reference speed representing a pseudo vehicle speed which is in turn compared with the actual wheel speed to prevent locking of the wheels. On the other hand, the predictive control is accomplished in such a manner that the surface condition of the road is determined by a deceleration sensor (hereinafter referred to as a G sensor) and a plurality of control patterns are predetermined, whereby the braking pressure is varied in accordance with the result of the determination by the G sensor to always suit the coefficient of friction between the road surface and the wheels. A disadvantage of the conventional system of this construction is that as the vehicle speed decreases, noise due to the wheel speed increases thus frequently causing erroneous controls at low vehicle speeds.